BELLEGARDE-SUR-VALSERINE, France, July 11, 2012 (AFP) —Tour de France leader Bradley Wiggins has hit out at critics who believe his and Team Sky's strong performances in the race are thanks in part to doping. "There's one reason I'm in this position and that's because I've worked hard," Wiggins said Wednesday.

Wiggins took another step toward becoming Britain's first yellow-jersey champion on Wednesday by defending his 1min 53sec lead on Australia's defending champion Cadel Evans on the first day in the Alps. But his team's performances in the hilly stages so far have prompted doubts among some keen observers and critics of the sport.

A day after their formidable pace-setting on the hilltop finish to stage seven gave Sky's Chris Froome the win and Wiggins the race lead several posts on the micro-blogging site Twitter questioned Team Sky's performance.

The posts compared its displays of fast pace-setting with the US Postal team of Lance Armstrong, the seven-time champion who has recently been charged with being part of a major doping conspiracy. A day after those posts, Wiggins let fly with a foul-mouthed tirade which, if anything, did little to substantiate his claims they have nothing to hide.

Sky, however, have done little to show its transparency. At a pre-organised press conference on Tuesday, all journalists were told questions on doping would not be tolerated or answered. Ahead of the first of three days in the Alps, Wednesday reports in the French press even referred to Team Sky as "UK Postal."

The first doping affair at the Tour—Frenchman Remy di Gregorio was arrested for allegedly trying to buy doping substances—has shown that cheating, even in isolated cases, still exists. But Wiggins, a three-time Olympic track champion who finished fourth in the 2009 race and was third at last year's Tour of Spain, said the doubts about him and his team are wide of the mark.

"I don't feel that I should have to sit here and justify everything I've done to the world," he said. "I'm not just some shit rider who's come from nowhere. I've been six-times world champion (on the track), fourth in the Tour de France, third in the Vuelta. It's not like I've just come from nowhere. I've got an incredible pedigree behind me."

Asked why he had lost his temper earlier this week when asked about doping issues, he replied: "To me it's them (critics) pissing all over everything I've done, by saying, 'yeah, he's cheating.' That's what really gets to me. Everyone in their individual jobs works hard at what they do.

"Yeah, I'm in the yellow jersey and I'm inspiring kids in the UK to take up cycling or whatever. But ultimately I've worked hard to be in this position and I deserve every minute of what I've been through in this last week or so, especially after sitting at home last year and watching it on the television."

Wiggins, who crashed out on stage seven last year, said he has passed dozens of tests by the anti-doping authorities.

"There's one reason I'm in this position and that's because I've worked hard," he added. "I'm tested by the UCI (International Cycling Union) God knows how many times a year, God knows how many times on this race and the Dauphiné (race), blood tested every morning.